Reference to quantum theory has become quite the fashion, and to base an expectation on an already receding episode with relativity theory, a great philosophical assault of interpretation of quanta is brewing in many quarters. The author of this series of studies would be content if by a plain statement of “what is the case” at this stage he could stem the more quixotic efforts, or rather reveal their unreal character to the spectators who may be enmeshed in the spell cast over such adventures. It is constantly necessary to restate the physicists' claims plainly in their positive content—as Einstein himself did once for relativity theory—so that one may know what is no-man's land and what is everyman's land in the new territory. This in itself is largely but a hope since there is no unanimity as to all the facts, and, worse, unanimity is no guarantee of stability. Nevertheless, the painstaking revision that is constantly going on on the experimental front enables us to arrange at least the data on a well-ordered scale of reliability. It then becomes much easier to detect false props to otherwise attractive theories, to discriminate live matter from the débris of progress, and to speculate on future growth. For such reasons the present examination of the various quantum theories will proceed from a presentation of facts and theories to their appraisal and then to a proposal concerning the organization of the facts, concepts and theories. The subject is very complex: There are several quantum theories, some of which are already referred to as “classical” although these themselves were anti-classical (anti-Newtonian); all have claimed success in their time; all have serious hiatuses, including the present. The author has chosen to hark back to some of the older issues before appraising the latest claims.
Reference to quantum theory has become quite the fashion, and to base an expectation on an already receding episode with relativity theory, a great philosophical assault of interpretation of quanta is brewing in many quarters. The author of this series of studies would be content if by a plain statement of “what is the case” at this stage he could stem the more quixotic efforts, or rather reveal their unreal character to the spectators who may be enmeshed in the spell cast over such adventures. It is constantly necessary to restate the physicists' claims plainly in their positive content—as Einstein himself did once for relativity theory—so that one may know what is no-man's land and what is everyman's land in the new territory. This in itself is largely but a hope since there is no unanimity as to all the facts, and, worse, unanimity is no guarantee of stability. Nevertheless, the painstaking revision that is constantly going on on the experimental front enables us to arrange at least the data on a well-ordered scale of reliability. It then becomes much easier to detect false props to otherwise attractive theories, to discriminate live matter from the débris of progress, and to speculate on future growth. For such reasons the present examination of the various quantum theories will proceed from a presentation of facts and theories to their appraisal and then to a proposal concerning the organization of the facts, concepts and theories. The subject is very complex: There are several quantum theories, some of which are already referred to as “classical” although these themselves were anti-classical (anti-Newtonian); all have claimed success in their time; all have serious hiatuses, including the present. The author has chosen to hark back to some of the older issues before appraising the latest claims.
For many years the physical interpretation of quantum theory has been dominated by the “wave-particle duality” attitude of the “Copenhagen school.” This point of view is eloquently described in Bohr's collection of essays on the subject. Despite persistent concerns with apparent paradoxes and limitations to this interpretation (as exemplified by Schrodinger's cat, the paradox of Einstein, Podolsky and Rosen, among others), the Copenhagen view persists de facto in the daily life of the modern physicist. Traditional quantum theory has so successfully explained such a vast amount of data in atomic and molecular physics, solid state physics (and to a lesser extent, elementary particle physics) that little doubt can exist concerning its essential validity. As a consequence of the overwhelming practical success of the “Copenhagen interpretation, ” the latter has acquired the status of dogma. For many years, therefore, most physicists have found it expedient to relegate the puzzling aspects of the theory to philosophers, and mathematicians. Nevertheless, a persistent interest in this subject has produced a significant and fascinating literature, reviewed by Jammer. In recent years, concerns over the proper meaning to be ascribed to quantum theory have produced an increasingly deep and incisive series of investigations. These investigations fall generally into two categories: either (1) discussion of the philosophical content of the theory, or (2) analyses of the mathematical variants of the theory and their connection with differing interpretational schemes. Physicists tend to be detached from a commitment to philosophical issues, because of their realization of the transient character of the meanings attached to theories of the day. As a simple illustration of this we can mention the profound differences between nonrelativistic and relativistic quantum mechanics.
The difficulties of the old quantum theory were largely dispelled by the development of quantum mechanics in the 1920s. First Heisenberg (1925) developed the rather abstract matrix mechanics and soon after Schro¨dinger (1926; see also Eckart, 1926) developed the physically more appealing wave mechanics. Subsequently he showed them to be mathematically equivalent. The physicists were greatly relieved; now they had once again a mathematical formalism that enabled the results of experiments to be calculated. It was possible to move forward. It is certainly a very elegant and indeed beautiful formalism, and does enable the results of many physical measurements to be calculated with great accuracy. It is used daily by atomic and nuclear physicists; there is no other way to make calculations. From the earliest days there has been intense debate about the interpretation of quantum mechanics, and it shows no signs of being settled; if anything it is becoming more intense over the years. As Penrose has remarked, no one understands quantum mechanics. Feynman (1967; see also Sykes, 1994) also admitted that ‘nobody understands quantum mechanics’, and Einstein once remarked: ‘I have thought a hundred times as much about the quantum problems as I have about general relativity theory’ (Pais, 1994, p. 57). It should therefore be evident that the most that can be done here is to try to show where the real difficulties lie, and how the failure to recognize that quantum mechanics is an essentially statistical theory has led to a series of confusing quantum paradoxes. It is just these paradoxes that have often been used to support theological speculations. It is useful to ask what ‘understanding quantum mechanics’ actually means. Certainly it means being able to calculate the results of many measurements. The same applies to Newton’s theory of gravitation, which we understand in the sense that we can use it as a basis of calculation, although we do not really understand the gravitational force itself. Very often, especially in modern physics, the mathematical formalism does not give us the sort of intuitive physical feeling for what is going on that we often obtain from classical mechanics. Perhaps we can never achieve more than this for quantum mechanics. In classical mechanics we can assume that a property that is measured objectively exists prior to the interaction of the measuring apparatus with the observed system. Quantum mechanics, however, ‘is incompatible with the proposition that measurement discovers some unknown but pre-existing property’ (Peres, 1997, p. 14). There is an important distinction between mysteries and absurdities. We may be forced to live with mysteries, but there is no reason why we should put up with absurdities such as the wave-particle duality, tunnelling through potential barriers, acausal events and the collapse of the wave function. These are the quantum paradoxes that will be discussed later on. They arise within the Copenhagen interpretation of quantum mechanics and are solved by other interpretations. These alternative interpretations enable us to make conjectures about what is going on, even though we cannot understand it in detail. This is acceptable and a stimulus to further research. It is certainly difficult enough to understand quantum mechanics, but there is no need to try to visualize logical absurdities in the effort to do so. Quantum mechanics is a mathematical formalism that makes it possible to calculate the results of some experiments. Anything more than this, such as questions about the interpretation of what is measured and whether it tells us what is actually going on in the system being studied, belongs to philosophy. Thus we are concerned here with what is essentially a philosophical debate; if it were just a matter of physics the debate would have been settled long ago. One of the difficulties is that it invokes the results of experiments and uses the language of quantum mechanics. Inevitably this language uses philosophical terms and then it is easy to give the impression that the philosophical propositions are in some way entailed by the physical results. These in turn can influence theological thinking. In order to be quite clear which arguments are justified and which are not, it is essential to separate the three levels of discourse: physical, philosophical and theological. Our task is to relate these together, and this immediately raises the traditional problems of the philosophy of science, including the relation of experiment to theory, and of theory to explanation. We begin by discussing experiments, distinguishing between those that are real and those that are imaginary.
Introduction Chapter 1 dealt with one of the deepest mysteries in modern science: how to explain consciousness. This Part deals with another mystery: how to make sense of quantum mechanics. Both involve a problem of reconciliation with the classical worldview, which is one hint that the two mysteries might be related. A second is that, unlike classical physics, which makes no reference to or allowance for consciousness, quantum theory raises the issue of consciousness and its relationship to the physical world in a very direct way. These hints do not necessarily mean there is a connection between the two mysteries, but by the end of this Part I hope to have shown why it would be natural to look for one. My more immediate aim here is to give the social scientific reader an introductory understanding of the experimental findings of quantum theory, its key concepts, and the debates about its interpretation. The discussion assumes no prior knowledge of quantum physics and makes no use of mathematics. Quantum theory without equations might seem like an oxymoron, and certainly reading this Part will not enable anyone to use quantum theory. But to a perhaps surprising degree it is possible to understand quantum theory without being able to use it. Its findings can be communicated in ordinary language, and the same goes for its main concepts and interpretive debates. One consequence of this has been the emergence of a virtual cottage industry of books on quantum theory for a lay audience. Most are written by physicists, and many are quite good. However, it is not just popular treatments that do without equations: much of the professional philosophical literature does as well. (I draw on both kinds of literature below.) Philosophers of physics are trained to understand the math, of course, which is necessary for a full appreciation of the issues.
Quantum theory has passed through three distinct stages during its evolution. The first is generally referred to as ‘old quantum theory’. During a period roughly between 1900 and 1925 Planck, Bohr and Einstein, among others, grappled with various experimental and theoretical crises by patching up classical mechanics with some new quantum ideas applied as band-aids. This is not to disparage the work; it was vitally important, and you can only do what is possible at the time. The quantum world is very different to the picture painted by classical physics. That being the case and given the extreme nature of some of these differences, we might question the wisdom of accepting the quantum view. Scientists can be quite disparaging about philosophy, sometimes while in the process of espousing, quite stridently, a philosophical position of their own. The chapter also presents an overview on the key concepts discussed in this book.
COGNITIVE ASPECTS OF THE HEISENBERG PRINCIPLE I T HE Heisenberg uncertainty principle, like its rival theory of relativity/ has been one of the truly crucial phases in the physics of our day~ It did not, like the discovery of a new element or the Maxwell equations, simply indent the story of classical physics for a new paragraph. It was not only a new chapter but a new book. Detected, in the words of Heisenberg himself, when physics became self-critical, the principle is a statement of what is observable-like its contemporary, the theory of relativity. It was anew advance in method, so revolutionary indeed that physics has virtually lost meaning as content and become synonymous , as logical empiricism amply indicates, with mere rules of procedure. That science is developing into a system of logic, combining the Cartesian stress on clearness with the Kantian regulative idea, actually confirms a contention of traditional philosophy. It reveals that once we deny the colors and sounds, the life, lights, and purpose in our universe-as pure scientific method actually does-we are fated to deny much more than quality. Quality is in the order of form, substance, and being. The moment quality is banished from the real world, by the same 1 That all is not as peaceful and unified in physics as the layman sometimes believes can be seen in the deep cleavage between quantum and relativity mechanics. For the first, the exact specification of space (position) and time (velocity, momentum) has no meaning, while in relativity theory such exact description is the only meaning that can be had. Despite the efforts 'of leading physicists, including Dirac, to unite the two theories, the contradiction is so profound that one of these systems must eventually be abandoned or, more probably, both of them will be superseded. The recent work .of Schroedinger and apparently also of Einstei~ himself are directed to extend the general theory of relativity, making the current theory a special case just as Newtonian physics is a special case of present relativity mechanics. 474 COGNITIVE ASPECTS OF THE HEISENBERG PRINCIPLE 475 decree being itself-because it is an immediate, non-inertial (formal) thing like quality-is driven into its only possible exile, nothingness. It is not surprising then that, after modern physics· has finished its task, the universe should not only be emptied of its lights, its fragrance, its sweetness, and its music but should also be without being and without existence. The uncertainty principle has been much debated in modern thought. Its impact has brought a sad end to the pride of 19th century science since it prevents a complete knowledge of anything at all by shading into the darkness at least one of the two major factors that specify it. Shortly after the principle was born it was hailed by various authors as a proof of free will, of the possibility of religion, and of non-mechanistic concepts in biology. In a more consistent and challenging sense, it has often been taken to refute what the physicist calls causality and what the philosopher calls the order of nature. The fact of the matter is that if the senses alone supply knowledge, truly only one thing at a time can be apprehended. If Hume was right in philosophy, so is Heisenberg. But when sensism yields to an intellectual insight into reality, it is easy to refute the scientist's claim to dethrone the doctrine of nature's order which he could never detect, even in classical physics, by pointerreadings .2 But whatever the fate of the Heisenberg principle in cosmology , it has had a most fruitful career in the field of physics. To Heisenberg himself, the principle was a point of departure for an original development of quantum mechanics based on the " uncertainty " of position and momentum,.: 3 If, for example, measurements are made, under a microscope, of the position of an electron, the photon (light-particle), which impinges on the eye and thus conveys the required knowledge to the physicist, has had to collide with the electron, thus imparting an impact known as the Compton recoil. When • For ·a discussion of the order of nature, cf. J. Marling: The...
THE GREAT CHAIN OF QUANTUM BEING: WHAT THE PHYSICISTS ARE TELLING US / Louis Gallo listen: there's a hell of a good universe next door; let's go —cummings Max Planck's announcement in 1900 that energy flows in discrete bundles rather than uniformly, as energy "should," did not instantly destroy the foundations of a classical world view that had prevailed since Newton's day. It took physicists nearly a quarter of a century to grasp the full significance of quantum theory. But 1900 is too convenient a date to ignore, and without distorting the history of ideas unduly we can refer to it as the point in time when science launched its relentless assault upon reason and common sense, an assault that continues to this day. This is nothing new, of course. Everyone knows how weird quantum theory is, how it toppled the Newtonian clockwork and so on. The purpose of this essay is to explain in ordinary language, if such a thing can be done, why physicists are saying some of the outrageous things we read about in the popular media. Because new particles, along with new theories to account for them, are being created at such a prodigious rate today, it has become extraordinarily difficult for non-scientists to keep up with the latest breakthroughs. The deluge of popular books on black holes and particle physics, outmoded before they go to press, reflects this information gap. I can hardly expect to beat the popularizers at their own game, but my intention is nevertheless to present a non-technical overview of the great chain of quantum being according to current theory. It can be suggested by way of preliminary assessment that the Theater of the Absurd did not die at some point in the early 1970s; its greatest production is and may always have been our meditations on the cosmos itself. We begin, however, with some thoughts on common sense rather than absurdity. Physicists have traditionally linked common sense with the twin doctrines of causality and determinism. Given thorough enough information about prior conditions, causality guarantees the predictability of all events and states ofbeing. French mathematician Pierre Laplace actually believed that such knowledge could be used to chart the entire history of the universe. Causality, then, is a way of thinking about individual events; determinism, a way of thinking about events 264 · The Missouri Review cumulatively. Both doctrines presume the existence of an objective, quantifiable external world populated by observers (ourselves). One cannot overemphasize the importance of the term "objective." It haunts modern physics at every turn. Indeed, the crucial difference between classical and quantum physics lies in their respective acceptance or rejection of objective reality. The early giants of quantum physics had a hard time accepting the implications of their own mathematics. Max Planck and Einstein—who is not, strictly speaking, a quantum physicist but who contributed much to the theory—refused to accept them. Yet the fate of objectivity may be traced by moving from Planck's position on the subject to that of Erwin Schrödinger, whose work culminated in the late 1920s. This chronology roughly reflects the order in which quantum theory emerged. Here is what Planck had to say in his book The New Science: "A science that starts off by predicating the denial of objectivity has already passed sentence on itself"; and "the quantum hypothesis will eventually find its exact expression in certain equations which will be a more exact formulation of the law of causality." Einstein spent most of his life searching for that "exact expression" and failed. Werner Heisenberg offered a similar but highly qualified version of Planck's statement. In Across the Frontiers Heisenberg says that quantum measurements do in fact measure objective states but also intrude upon those states. "It is," he writes, "no longer the objective states but rather the probabilities for the occurrence of certain events that can be stated in mathematical formulae." Schrödinger, in Mind and Matter, comes right out with it: "Mind has erected the objective outside world of the natural philosophers out of its own stuff." He means this literally, and the equations he contributed to quantum theory imply as much. Bohr...